Tips for Drill Bits

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Tips for using drills: Just a short collection of tips and advice for getting the most out of your drill and drill bits.  Best regards, denver00

  • ·    For drilling larger holes it is best to do them in stages. Start with a smaller drill bit, & then work up to the final size using progressively larger drill bits. This will reduce the strain & wear on the drill & drill bit, & reduce the chance of you ending up with a triangular shaped hole.
  • ·    Before attempting to drill a hole in metal first scribe two perpendicular lines intersecting to mark the required hole centre, & make a deep centre-punch mark to stop the drill point from skating around.  Do this in 3 stages; first make a light centre-punch mark exactly where the lines intersect. Next inspect the mark, & you will invariably find that it is slightly off from where you intended it to be. Worry not, you can move the punch mark to where it should be by driving it across the surface with light hammer blows applied to an angled centre punch. When you are satisfied the mark is correctly positioned, set the centre-punch vertical and give it a good whack to make a nice deep indentation.
  • ·    Take care if drilling through thin sheets of metal. Make sure the sheet it is well fixed in position, otherwise it is quite easy for the drill bit to snatch the work as it breaks through. This can result in a nasty cut if a metal sheet spins out of your grip, so do not hold it in bare hands, but clamp it firmly to the bench!  Drilling sheet metal into a block of scrap wood (MDF is ideal) will result in a cleaner exit hole & less chance of the metal climbing up the flutes of the drill bit immediately after breakthrough. For best results sandwich thin sheet between two pieces of wood.
  • ·    Many metals need to be drilled at relatively low speeds in the 300 - 900 rpm range, so many standard mains drills are too fast, resulting in an overheated drill bit. A workaround for this is to drill for 10 to 20 seconds, then rest to allow cooling, & then repeat.
  • ·    Materials likestainless steel require low speeds with very high drill pressures to prevent the drill from simply polishing the hole. To get best performance with hard metals it is often helpful to put the pressure on before starting the drill. When you want to stop drilling, keep the speed up & quickly remove the drill bit from the work. A cutting oil is required for larger drilling jobs to lubricate & cool the work.
  • ·    Soft metals such as pure aluminium are an exception to the slow speed rule, because these build up swarf that sticks to the cutting edge. A fast rotation speed reduces this problem, if used with a slow feed rate.
  • ·    In general, the best rotation speeds for various drill sizes & feed rates depends very much on what is being drilled and by what tool. For example when drilling very hard steel, it is necessary to apply lots of pressure to the twist drill. On the other hand, aluminium, copper & brass are better drilled at a slower feed rate, but quite a fast rotational speed.
  • ·    A useful trick if drilling holes in walls indoors is to tape an envelope to the wall just beneath the hole you are drilling to catch all the dust falling from the hole and save you a cleanup job.
  • ·    How do I stop my drill bit from slipping in the chuck?  First of all, try using less pressure.  Let the drill do the work.  Slow & steady is often the trick to achieving a good result.
  • ·    Holding the Drill:  Use two hands on your drill, one on the trigger handle to take the weight & (try to) keep the drill bit vertical, & the other hand at the back of the drill to apply pressure in line with the drill axis. Take care not to cover the ventilation slots with your hands.
  • ·    DO NOT force the drill: For a 10mm diameter drill bit you should use about 15lbs (7kg) of force & let the drill do the work. For smaller drill bits, reduce this greatly, for a 2mm drill bit, under a kilo may be appropriate.
  • ·    Lubrication: Drilling in metal needs lubrication of the drill bit, ideally with proper lubricating fluid, but failing that 3-in-1 oil or cooking oil is a lot better than nothing.
  • ·    It is important to be sure that you do not drill into any services (gas, water, electricity, phone lines, etc). Assume that wires and pipes may be buried anywhere in a wall (very true in older houses).  Pay particular attention when drilling holes either vertically or horizontally in line with any electrical fitting like a light switch or socket, since this is a very likely place for the cable to run. Also be aware that the 150mm strip of wall beside any corner, & adjacent to the ceiling are also allowable zones for buried wiring in the UK wiring regulations (BS7671).
Best regards

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